Thermal bridges

OPET Czech Republic OPET CR

Publication

Organization for the Promotion of Energy Technologies

Thermal bridges

in residential buildings in Denmark A part of the OPET work package: RUE in prefabricated buildings

ENERGIE

Brno 2002

OPET Czech Republic OPET CR Organization for the Promotion of Energy Technologies ENERGIE In 1990 the EC launched the THERMIE Programme focused on demonstration of non-nuclear energy technologies. At the same time a Network of Organisations for the Promotion of Energy Technologies (OPET) was established to help the Commission with the dissemination of information on project results and the promotion of new technologies in the field of non-nuclear power engineering. Since November 1996 the OPET Network has been managed as a co-operative venture between DG XVII and DG XIII. In 2000 the OPET Network was extended to cover similarly oriented organisations in the Countries of Central Europe (CCE), Candidate Countries and a number of countries who have signed international co-operation agreements in the field of RTD with the EU. In June 2000 the OPET Network consisted of 45 consortia operating in Europe and other countries. The Czech Republic is a member of the OPET Network through the OPET CR. The OPET Network is unique structure connecting the demonstration and innovation part of former European programmes JOULE-THERMIE and INNOVATION with current ENERGIE programme that is a part of the 5th Framework Programme (19982002). This connection makes it possible to cover both research and demonstration activities related to the support of technology transfer and to put into practice the results of RTD in the field of energy technologies and innovations. The main task of the OPET Network is to collaborate with organisations, institutions and companies and help them in their search for and exploitation of clean and energy effective technologies, particularly those resulting from projects supported by the EC under the energy oriented programmes. The objective of all activities is to support dialogue between countries, clients, and to try to understand problems and needs and help to find innovative technology solutions. The basic idea of the OPET Network also includes a wide discussion on the future of European technology research and development realised in close collaboration with practical needs of clients, particularly under the 5th Framework Programme and other energy-oriented programmes. The OPET CR had supported in the framework of its international activities the collaboration between the teams from Denmark and the Czech Republic in their work on this publication.

OPET Czech Republic OPET CR is a member of a network based by European Commission for the promotion of efficient and innovative energy technologies

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Technology centre AS CR Rozvojová 135 165 02 Praha 6 Czech Republic (+420 2) 203 90 712 (+420 2) 209 22 698 [email protected]

KEA Energetická agentura Durïákova 49 613 00 Brno Czech Republic (+420 5) 452 11 974 (+420 5) 452 11 974 [email protected]

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Thermal bridges in residential buildings in Denmark A part of the OPET international work package: RUE in prefabricated buildings

Brno 2002

Written by: Lars Olsen Division for Building Technology, Niels Radisch Division for Energy Technology Danish Technological Institute Graphics: grafické studio Klassic, s. r. o., Norbertov 53/5, Praha 6-Dejvice Published in the frame of the project of European Union OPET Czech Republic OPET CR (Organization for the Promotion of Energy Technologies, Czech Republic) Text Grafics Published

© Lars Olsen, Niels Radisch © grafické studio Klassic, s. r. o., Norbertov 53/5, Praha 6-Dejvice © KEA energeticka agentura s. r. o., Brno, Technology centre AS CR, Praha

LIST OF CONTENTS 1. Introduction

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2. Conclusion

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3. The building regulations, standards and reports

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3.1. The Danish Building Regulations

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3.2. Standards

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3.3. Reports

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4. Types of residential buildings in Denmark

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4.1. Typical designs of residential buildings

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4.2. Typical residential houses according to material of periphery walls

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5. Thermal-technical defects thermal bridges

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5.1. Geometrical thermal bridges

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5.2. Structural thermal bridges

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5.3. Systematic thermal bridges

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5.4. Convective thermal bridges

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6. Negative consequences of thermal-technical defects

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6.1. Energy related consequences

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6.2. Other consequences

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7. Examples of solutions of defects

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7.1. Additional insulation on the outside

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7.2. Cavity wall insulation

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7.3. Additional insulation on the inside

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7.4. Other measures

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8. References

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OPET CZECH REPUBLIC OPET CR

1. INTRODUCTION The present report is the Danish contribution to the OPET work package "RUE in prefabricated buildings", led by OPET Czech Republic. The Danish part is about residential buildings and is to some extent based on Nordic work on thermal bridges. At a meeting in Prague April 19, 2002, the Danish contribution was gone through, and this present report includes what was agreed at the meeting. Since the 1970s Denmark has set up some of the most extensive/ambitious building regulations concerning the insulation of the building envelope. By doing this, concern has also been given to thermal bridges, as they become increasingly important by low U-values.

· European standards · Residential buildings in Denmark The chapters 57 describe thermal bridges more generally: · Different types of thermal bridges · The consequences of thermal bridges · Examples on solutions To improve the building envelope by reducing thermal bridges, the calculations as well as the building techniques should not be too complicated. Another important point is that the demands on the energy performance of the buildings have to be backed by the building regulations.

The chapters 34 of the report describe the situation concerning: · Danish building regulations and standards · Reports including one common Nordic report

Danish Technological Institute Lars Olsen & Niels Radisch

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Thermal bridges in residential buildings in Denmark

2. CONCLUSION A Nordic study showed that the transmission loss is likely to increase by 1050% when more correct calculations of thermal bridges are introduced. It is especially thermal bridges in the walls around doors and windows, which increase the overall transmission loss. During the last years, attention has been given to thermal bridges in windows. By reducing the width of the window frames and improving their insulation the total U-values of windows have been improved by 1030%.

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The intention further to reduce the energy consumption in the building sector puts more focus on the thermal bridges. Calculations show that when no attention is given to thermal bridges in low energy buildings, the thermal bridges can amount up to more than 60% of the total transmission losses. This report shows the large influence of thermal bridges, but it also shows that there are good possibilities to reduce the amount of them and at the same time improve the thermal comfort in the buildings.


3. THE BUILDING REGULATIONS, STANDARDS AND REPORTS 3.1. The Danish Building Regulations The Danish Building Regulations consist of 2 parts: · one for smaller houses as one family houses and row houses (BR98-S) · one overall part covering all other buildings (BR95) Both are divided into chapters covering the different areas of a building project. In chapter 8 "Thermal insulation" the following about thermal bridges is pointed out: 8.1.2: External building parts, including windows and doors, are due to the risk of condensation only allowed to have an unessential amount of thermal bridges. The ener-

gy related influence of the thermal bridges must be taken into the calculation of the thermal transmittance (U value) for the individual building parts. 8.1.3: Buildings and parts of buildings, including windows and doors, must be done in a way ensuring that the heat losses are not essentially increased due to moisture, wind or unintended penetration of air. In 8.1.6 the Building Regulations refer to DS 418 (Danish guidelines for calculation of heat loss).

3.2. Standards 3.2.1. European standards A number of European standards are published to provide ways of calculation and measuring heat losses. Thermal bridges are an important part of these standards. One calculation system is described in EN ISO 14683. It divides the transmission heat loss from a building into

one part with undisturbed construction with onedimensional loss, another part with linear thermal bridges taking two dimensional heat flow into consideration and a third part with point thermal bridges taking three dimensional thermal heat flow into consideration.

Figure 1: Surface, line and point elements

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Large emphasis is laid on setting up calculation models to do calculations with sufficient accuracy (EN ISO 10211-1 and 2). The standards leave different options to apply different sets of dimension systems. The dimension system and also the definition have influence on the numerical value of the thermal bridge. The two principal types are external and internal dimensions. Applying external dimensions for external edges will lead to significant smaller linear thermal transmittances than if internal dimensions are used. For external edges the value can in some cases even be negative. In these cases the value is assumed to be zero. In one standard (EN ISO 14683) a set of default values is given. The values are general and do not include many details. The values of the linear thermal transmittance include the total heat loss through the thermal bridges but subtracted the one dimensional heat loss corresponding to the undisturbed part of the construction.

One of the standards covers heat loss through the foundation (EN ISO 13370). The method is based on a dynamic analytical method and takes the size of the floor into consideration. The standard assumes that the heat flows through the floor, the soil to the exterior ground surface. By doing numerical calculation in combination with the method, it is possible to apply the method also to special foundation constructions. But very few default values for the joint floor-wall are given in this standard. So the user will often have difficulties in achieving accurate values without doing detailed calculations. The CEN standards have given the general guidelines for estimating the effect of thermal bridges, but have not given a comprehensive set of values for the different thermal bridges.

3.2.2. Danish standard "Rules for calculation of Heat loss from Buildings" The Danish standard DS 418 "Rules for calculation of Heat Loss from Buildings" /4/, provides a simple and practical method for assessing heat loss. It is the key-standard for the calculation of heat losses from buildings to check if the transmission loss observes the Danish building regulations. A revised 6th edition of DS 418 is expected to be available May 2002. The standard has adopted the new EN-standards. This is made in a way to reduce the amount of written pieces of information which the user has to go through to be able to apply the standard. Furthermore the standard is supplemented with a number of default values for the most important construction types in typical Danish buildings. The standard is primarily used as a basis for the calculation of the annual energy performance of buildings, while the calculation of the losses for the design of the heating system is expected to be covered by other standards. Below parts of DS 418, which might be of special interest to other countries, are summed up. The dimension system is changed to primarily external dimensions. The advantage is that in a number of cases the heat loss will be on the safe side, i.e. the losses will be larger than if a more accurate calculation was made. The standard has a number of tables with the linear thermal transmittance for thermal bridges. The values are based on

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the total heat loss through the construction with the thermal bridge but after subtraction of the different (local) one dimensional heat losses. These one dimensional losses come from both the undisturbed part of the construction and from parts where thermal bridges occur. This method is slightly different from the tables in the EN-standards, where there are bigger differences between tabulated values due to another definition of the construction parts. Tables of the linear thermal transmittances in the windowwall joint are organised in dependence of the materials of the walls and the thickness of the thermal break. The calculation of the thermal loss through the ground is based on a calculation of the dynamic loss through the ground. The external temperature is assumed to be varying sinusoidal corresponding to the annual variation. A model of the floor construction is set up including a part of the ground. The heat loss through the construction is calculated until quasi-stationary equlibrium is obtained typically after a number of sinusoidal periods. The linear thermal transmittance of the foundation is calculated as the total heat loss in the heating season subtracted by the one dimensional heat loss through the different construction parts. The one dimensional heat flow through the floor is defined to be the same for the whole floor as the heat flow in the centre of the building. In the standard, linear thermal transmittance is given for typical Danish foundation details.


3.3. Reports In Denmark different reports dealing with thermal bridges are elaborated.

methods give normally the lowest accuracy, if the values do not cover the actual type of construction.

The aim of the NKB /1/ report is to introduce the concept of thermal bridges and outline the consequences of including thermal bridges in the calculation of heat loss from buildings. Different thermal bridges are defined. This is described in a later chapter 5. The calculation principles and guidelines on calculation of thermal bridges are described. The contribution of thermal bridges to heat loss is compared with the total transmission loss from typical Nordic Buildings. In the report different default values of thermal bridges are suggested. The effect of thermal bridges can be estimated by different accuracy. Simplified

Another report /3/ contains an overview of 12 different external post insulation systems. The different systems are evaluated regarding construction, thermal insulation, durability and economy. The third report /2/ is concerning design of new low energy houses. The report contains information on how to take a number of aspects into consideration in order to obtain a low energy house. In the field of thermal bridges it is especially air tightening of buildings which are of interest.

3.3.1. NKB In an example of a calculation which demonstrates the significance of thermal bridges in typical Nordic Buildings it is shown that the transmission loss is likely to increase by 1050 %, if thermal bridge calculations are introduced in conformity with the CEN standards. The thermal bridge increment to a high degree will depend on how well the thermal bridges are detailed, and how well insulated the buildings are. In particularly it is the thermal bridges in the walls around windows and doors and through foundations, which make a large contribution to the aggregate heat loss. On the other hand, thermal bridges through vertical junctions between walls normally make only a small contribution. It is considered that EN standards can be used for thermal bridge calculations, but that there is a need to modify and adapt them, so they should not be too complicated for the use by designers.

The tabulated values prepared by CEN are not well suited for the structures used in the Nordic types of structures. Where special structures are used, either tables with values on the safe side can be used or two-dimensional calculations can be performed for the structure concerned. These two-dimensional calculations involve additional work, but there are computerised catalogues available which should make this work a lot easier. Calculations for three dimensional thermal bridges are normally not necessary. It is necessary to establish a dimension system, as the EN standards are optional in this respect. Application of EN standards will necessitate guidelines and information activities, since calculations for thermal bridges will be a new approach for most consultants.

The actual calculations of thermal bridges should not be particularly time consuming for the designers, when they make use of tabulated values for thermal bridges.

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4. TYPES OF RESIDENTIAL BUILDINGS IN DENMARK 4.1. Typical designs of residential buildings The following building designs used in Denmark are covered by the Building Regulations for Small Houses (BR 98-S): · Single-family houses · Double houses (beside each others) · Row houses The Building Regulations (BR 95) comprises: · Two-storey houses with one apartment above the other · Multi-storey apartment blocks In the year 2001 a total of 17,400 dwellings were built in Denmark 6,000 as private single family houses, 4,000 as

private or social double/row houses and 7,400 as private or social apartments in blocks. Traditionally houses in Denmark are made out of bricks which are manufactured from clay, which is found in the underground. One important reason for that is fire protection. A minor part mostly smaller, newer ones are made in a Swedish style out of wood. Experiments have been carried out with wooden constructions in bigger houses.

4.2. Typical residential houses according to material of periphery walls In Denmark many different combinations of constructions are used for houses in the residential sector. Traditional buildings from before 1950 are typically made out of masonry. For many years as cavity walls, but in the beginning without insulation in the cavity. Many of these have later been supplementary insulated by injection of granulated insulation. A number of dwellings are made of concrete structures, especially in the 70s and 80s, with insulation sandwiched in the structure. The external part was often made of concrete covered with tiles. Later constructions are often made with

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an inner wall to which insulation and external cladding are added. During the last 2030 years the inner walls are made out of lightweight concrete either of autoclaved aerated concrete or concrete with aggregate of expanded clay. The insulation material used in walls is typically of mineral wool. The cladding can be bricks, wood or many types of boards. The insulation thickness in the constructions has increased during the years according to the different building regulations.


5. THERMAL-TECHNICAL DEFECTS THERMAL BRIDGES Thermal bridges come from the design and building phase. In this project mainly the design based thermal bridges are mentioned. 1. 2. 3. 4. 5.

On the following pages types 14 are described in details. The most common reasons for thermal bridges are explained. A combination of different types of thermal bridges occurs very often in the same building component.

Geometrical thermal bridges Structural thermal bridges Systematic thermal bridges Convective thermal bridges Air tightness problems

5.1. Geometrical thermal bridges Geometrical thermal bridges are found where there is a change in the direction of the surfaces forming the building

envelope or where the thickness of these surfaces is locally reduced. Examples are heat loss at edges and corners.

Figure 2: Examples of geometrical thermal bridges. Corner and step in surface At the corners and edges of a building, a thermal bridge occurs at the junction between wall and ceiling, wall and wall, and wall and floor. At these places the geometrical thermal bridges are due to changes in the direction of the

building surfaces. Geometrical thermal bridges can be approximately taken into consideration in calculations if, at external edges, the external dimensions are used instead of internal dimensions.

5.2. Structural thermal bridges Structural thermal bridges are due to deliberate penetrations of the building envelope. Examples are penetrations for

services between the cold and warm sides and junctions between different building components.

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Figure 3: Examples of structural thermal bridges. Junction between wall and balcony slab and penetration for services Typical examples of structural thermal bridges are: · Points where e.g. projecting beams and slabs pass through the building envelope between the cold and warm side of the building. · Openings in walls for windows and doors.

· Penetrations for various services such as water pipes, chimneys, ventilation ducts and cables. · In many cases structural thermal bridges are not taken into consideration, when the heat losses from the buildings are calculated.

5.3. Systematic thermal bridges Systematic thermal bridges are a special type of structural thermal bridge. These are repeated in a specific pattern, so

that the structure can be designed for purposes of heat loss as a structure with one dimensional heat flow.

Figure 4: Examples of systematic thermal bridges. Wall ties and timbers in stud walls. Systematic thermal bridges occur in many building components. They may be due to wall ties or joints in masonry, or to timbers in stud walls. This type of thermal

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bridges is normally allowed for in a simplified manner in calculating heat losses from buildings.


5.4. Convective thermal bridges Air movements inside the construction cause convective thermal bridges.

possible for heat losses to increase if outside air can be blown through the insulation.

The term convective thermal bridges is used here to denote places in structures where unintended air movements occur inside the structure. These may be due to natural convection in gaps, through gaps or in the insulation itself, or between gaps on each side of the insulation. It is also

Finally room air may also pass into the structure. This air stream gives rise to a heat loss which is included in the ventilation loss. But the air stream will also cause moisture to accumulate in the outer part of the building envelope, with a reduction in insulation performance as a result.

Figure 5: Examples of convective thermal bridges. Natural convection around the insulation and penetration of outside air into the attic. These types of thermal bridges are at present allowed for by way of general increment of either conductivity or thermal transmittance. Convective thermal bridges are not given detailed treatment in the standard EN ISO 6946.

There is only limited knowledge regarding the extent of this type of thermal bridge in practice. In some cases there is a additional heat loss where outside air can penetrate below the roof insulation. Convective thermal bridges can be greatly reduced by proper design and workmanship.

Figure 6: Thermographic picture showing a convective thermal bridge due to air infiltration below the insulation (joint between the roof and wall)

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6. NEGATIVE CONSEQUENCES OF THERMAL-TECHNICAL DEFECTS 6.1. Energy related consequences Low energy constructions are sensible to thermal bridges. To illustrate the proportion of the total transmission loss through the building envelope, which is due to thermal bridges, calculations have been made /1/. Ventilation losses are not included in these calculations. The thermal bridges are divided into 3 groups: · low value if great care is taken to reduce heat losses · medium value typical design · high value when a structure is built with a large thermal bridge, e. g. a solid construction between the front and rear leaves of a wall In the same way as for the structural details, three levels of transmission loss (U-values) are set out: · low value typical for low energy constructions · medium value corresponds to the Danish building regulations · high value represents a substantially larger heat loss than the medium value (as the 1970s) In this way 2 buildings have been calculated one single storey building (floor area 120 m2 windows + doors 21,6 m2) and one 3-storey building (floor area 432 m2 windows + doors 265 m2). The most important results show that: · Thermal bridges around the windows (not the panes) give the largest individual contribution (3148%).

· The heat loss from the junctions of the external walls is in the low end (13%). · The heat loss through the windows gives the biggest contribution to the total heat loss. · In older Danish buildings (high value) with average thermal bridges the proportion of heat loss from thermal bridges for both building types is 1920%. · With a modern Danish insulation standard (medium value), but unchanged (medium value) thermal bridges, their contribution will rise to 3032%. With heavy thermal bridges (high value) the contribution will be 58%. With minimum thermal bridges their contribution will be reduced to 13%. · In low energy buildings (low value) with average thermal bridges the proportion of heat loss from thermal bridges for both building types is 4851%. With a modern insulation standard (medium value) but unchanged thermal bridges, their contribution will amount to 3032%. It is evident that it is important to assess linear thermal bridges where there are a lot of these around windows and along horizontal lines, while the contribution due to external vertical edges on walls is normally moderate.

6.2. Other consequences Besides the additional heat costs caused by thermal bridges, there are consequences for the following items: 1. Health 2. Maintenance 3. Comfort Thermal insulation normally has the greatest relative significance for heat loss in new buildings. When the insulation is very thick, thermal bridges have a great relative significance for the total heat loss. In new buildings

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low temperatures occur mostly around windows and at penetrations for services. Thermal bridges also have considerable significance in existing buildings. When supplementary insulation is installed, it is generally easier to reduce the extent of thermal bridges, if the insulation is applied on the outside, than if fitted on the inside. Generally speaking, supplementary insulation applied on the outside will always raise the surface temperature on the inside. If supplementary insulation is fitted on the inside,


there will often be isolated areas on the inside of the building envelope, where the surface temperature is lower than before supplementary insulation. In order to avoid condensation in buildings with severe thermal bridges, it is necessary to ensure that relative humidity in the room is sufficiently low. This is achieved by making sure that production of moisture is low, and that there is a sufficiently large rate of air change. In the case of supplementary insulation on the inside, there may also be a risk that the air change rate has to be increased; this may give rise to increased energy consumption. In existing buildings there are a number of problems at present due to a level of humidity that is too high in relation to moisture production, air change rate and the class of thermal bridge. If the surface temperatures were higher, these problems would be more limited in scope.

Maintenance and health The consequences of condensation or a very high relative humidity at the surfaces are that the maintenance requirement is increased, because surface treatment has to be applied more frequently. Another problem with condensation is the risk for mould growth causing allergy and other health problems. Comfort Thermal bridges can also cause thermal comfort problems. If there is large poorly insulated or uninsulated areas of the walls, the surfaces will be cold in the winter which can cause cold draughts. Leakages in the building envelope can also lead to draughts. The cold draughts will cause low floor temperatures. The cold draughts and low surface temperatures can both give thermal comfort problems.

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7. EXAMPLES OF SOLUTIONS OF DEFECTS The measures mentioned are normally used on existing buildings.

7.1. Additional insulation on the outside Two examples of systems are shown. The first one is produced by Rockwool and is a system where the insulation is mounted by bolts. The insulation is covered by a layer of 7 mm of plaster. The second example is produced by Danogips. The insulation is mounted in a set of metal profiles which are sliced in order to reduce the thermal loss. A number of different materials can be used as external cladding. In a list of 12 different insulation systems /3/ the results show, due to variation of the system for mounting, the thermal resistance with 100 mm insulation can vary between 2,0 and 2,65 m2K/W.

Figure 7: Examples of insulation on the outside

7.2. Cavity wall insulation Insulation of cavities in brick walls in existing buildings is common as a supplementary insulation. The insulation type is normally of mineral wool or granulated polystyrene.

The insulation is injected by such a high density that settings are eliminated. A control scheme during the years has secured and shown high quality of the work.

7.3. Additional insulation on the inside Internally placed supplementary insulation /5/ has the advantage of not changing the appearance of the exterior facade and being relative easy to apply. The interior surface does not need to be able to withstand the same climatic exposure as at the exterior. This means that it in principle will be able to provide this type of insulation at a lower cost. The drawbacks are the increased risk of condensation problems, the reduced area for living space and the lower

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efficiency of the installation due to thermal bridges from projecting inner walls and floors. The thermal bridges both can be from conduction in the wall/floor and from a convective thermal bridge e. g. external air penetrating the existing exterior wall. The increased risk of condensation is due to the lower surface temperatures of the existing surfaces, which are not covered by the internal insulation. In some cases it is necessary to increase the ventilation rate to decrease the humidity in the air.


Figure 8: Examples of insulation on the inside

7.4. Other measures 7.4.1. Air tightening It is possible to tighten air leaks in the building envelope. In many cases it is difficult, e. g. that electric installations are not designed to be airtight. By careful planning of the placement of the plane of tightness in the construction

it will be possible to reduce the penetrations of the building envelope /2/. The drawback is that the building might be too airtight leading to a high relative humidity indoors.

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8. REFERENCES 1] The significance of thermal bridges for heat loss from buildings. L. Olsen, G. Jóhannesson. Nordic Committee on Building Regulations, NKB, Energy Committee, NKB Committee and Work Reports, 1996: 10E. 2] Design of low energy buildings, A collection of experiences from low energy buildings. (in Danish), L. Olsen. Byggeteknisk Institut, Dansk Teknologisk Institut, Laboratoriet for Varmeisolering, Danmarks Tekniske Hojskole, Energiteknologi, Dansk Teknologisk institut. September 1993. 3] Catalogue of supplementary insulation systems. An overview and comparison of supplementary insulation systems with possible product developments. (in Danish), Institut for Bygninger og Energi, Danmarks Tekniske Universitet. Rapport R-21, 1998. 4] DS 418, Rules for calculation of Heat Loss from Buildings, (in Danish), 6. Edition. Dansk Standard. Expected to be published. May 2002. 5] Interior supplementary insulation. Moisture- and temperature conditions of joist ends placed in masonry (in Danish). H. J. Krebs, P. F. Collet, Byggeteknik, Teknologisk Institut. 1982. 6] Outdoor Postinsulation of Facades, General description, A. Damsgard Olsen, H. Samuelsen. Building Technology. The Technological Institute of Copenhagen. 1984. 7] Outdoor Postinsulation of Facades, Catalogue, P. Andersen. Building Technology. The Technological Institute of Copenhagen. 1984.

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EN ISO 6946, Building components and elements Thermal resistance and thermal transmittance Calculation method. (ISO 6946). EN ISO 10211-1, Thermal bridges in building construction Heat flow and surface temperatures, Part 1. General calculation methods (ISO 10211-1). EN ISO 10211-2, Thermal bridges in building construction Calculation of heat flows and surface temperatures, Part 2. Linear thermal bridges (ISO 10211-2). EN ISO 13788, Hygrothermal performance of building components and building elements Internal surface temperature to avoid critical surface humidity and interstitial condensation (ISO 13788). EN ISO 13789, Thermal performance of buildings Transmission heat loss coefficient Calculation method (ISO 13789). prEN ISO 13790 Thermal performance of buildings Calculation of energy use for heating (former EN 832). EN ISO 14683:1999 + AC, Thermal bridges in building construction Linear thermal transmittance. Simplified methods and default values. (ISO 14683). EN ISO 13370, Thermal performance of buildings Heat transfer via the ground Calculation methods (ISO 13370: 1998).

ISBN 80-902689-6-X